Galvanized Steel Reinforcement for Concrete

 

When steel reinforcement in concrete corrodes, the corrosion waste product occupies more than three times the volume of the original steel. This exerts tremendous forces leading to cracks, introducing more weather access and further corrosion. In mild cases, rust staining occurs. In serious cases, severe spalling breaks up the concrete and may result in the failure of the concrete member.

 

The benefits of galvanized reinforcement include the protection of the steel during storage prior to installation, safeguards against poor workmanship in relation to misplacement and inadequate curing, delayed initiation of corrosion and the onset of cracking, reduced chance of surface staining, and increased structural life of concrete.

 

Environmental agents like oxygen, water, carbon dioxide and chloride ions are the common causes of corrosion in black steel reinforcement.

 

Marine structures are exposed to highly corrosive chloride ions in sea spray and salt-laden air. Away from coastal environments, carbonation is the primary cause of corrosion in reinforcement which has the effect of reducing the alkalinity of the surrounding concrete.

 

Studies have shown the tolerance of galvanized reinforcement to chlorides is substantially higher than that of black steel in marine structures. With its greater range of pH tolerance, galvanized reinforcement outperforms black steel for carbonation resistance.

 

Recent studies have shown that the additional cost of using galvanized reinforcement adds between 1.5 to 3.0% to the building's total cost. And in most structures, even in harsh marine environments, the use of galvanized reinforcement can be limited to exposed surfaces and critical structural elements like facades, exposed columns, and window and door surrounds. This can further lower the additional cost of using galvanized reinforcement to as little as 0.5 to 1.0% of the building's total cost.

 

The extra cost of using galvanized reinforcement could be considered an 'insurance premium' - a one-time payment that may be small when compared to the expense and risks caused by corrosion damage. In recent cases, repair costs to fix the damage caused by unprotected reinforcement on major buildings have been as high as 5.0 to 10% of the original building costs. Such repairs may only address the visible damage and may not have ensured a long-term solution.

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